Projection-type photolithography systems are widely used in current integrated circuit manufacturing processes, wherein a size-reduced image of a pattern on a mask plate is projected on a substrate surface using a projection objective lens and then the pattern is transferred by means of other processing steps. A core structure of an existing projection-type photolithography system is shown in FIG. 1, comprising a lighting system 1, a mask plate 2, a projection objective lens 3, and a substrate 4. The lighting system 1 is located at the top of the system, and functions as an incident light source of high quality. The mask plate 2 is located below the lighting system 1, and provides an object to be imaged by the projection objective lens. The projection objective lens 3 is located below the mask plate 2, and performs imaging. The substrate 4 is located below the projection objective lens 3, and receives the result of imaging and then is used in subsequent processing steps. Distances between the mask plate 2, the projection objective lens 3, and the substrate 4 satisfy the object-image relationship in lens imaging.
The projection objective lens requires a very large numerical aperture and a very high imaging quality in order to achieve a high imaging resolution, because the imaging resolution is proportional to the numerical aperture of the projection objective lens, and meanwhile aberrations of the lens will reduce the imaging resolution significantly. These propose harsh requirements to the designing, processing and assembling process of a projection objective lens system having a large numerical aperture and a weight of over one ton.
In contrast to the projection-type photolithography systems, direct writing photolithography systems do not need a mask plate, but instead utilize focusing elements to obtain very small light spots, such that a pattern is formed directly on a substrate. Zone plate maskless direct writing systems and photon sieve maskless direct writing systems utilize a zone plate and a photon sieve as the focusing element, respectively, to obtain the very small light spots. Because the zone plate and the photon sieve are used instead of the complex and costly projection objective lens, the zone plate maskless direct writing systems and the photon sieve maskless direct writing systems both can effectively reduce manufacturing cost as well as volumes of the photolithography systems.
However, both the zone plate maskless direct writing systems and the photon sieve maskless direct writing systems belong to the direct writing photolithography systems, making them incapable of performing photolithography in batches rapidly by using the mask plate, and thus their efficiencies are much lower than that of the projection-type photolithography systems.